1. Technical Field
The present invention relates to an image forming apparatus.
2. Description of Related Art
In an electrophotographic image forming apparatus, control parameters of a fixing unit for heating and fixing a toner image onto a paper (a sheet of paper) are changed according to the type of a paper on which an image is formed. For example, when a paper is a thick paper, the temperature of a heating roller is set to be high as compared with the case in which a paper is a plain paper.
In relation to this, Japanese Unexamined Patent Publication No. 2008-180947 discloses a technology of measuring the temperature of a heating roller before and after one paper passes through a fixing unit and determining the type of the paper from a temperature gradient. According to this technology, it is possible to automatically determine the type of a paper and determine control parameters of the fixing unit.
However, in this technology, since a small temperature change when one paper passes through the fixing unit is measured, there is a possibility that the type of the paper cannot be determined correctly. On the other hand, a temperature change when a plurality of papers pass through the fixing unit is also considered to be measured, but if a time for determining the type of the paper is too long, since a time until the state of the fixing unit is stabilized also becomes long, it is not preferable.